package com.gitee.huanminabc.jcommon.encryption;

import com.gitee.huanminabc.jcommon.exception.BizException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * RSA加密  非对称加密
 */
public class RSAUtil {

    // 一般后端生成公秘钥和私密钥,  将公秘钥给前端进行加密内容,后端拿私密钥解密

    /**
     * 前端 jsencrypt.js
     *
     * 链接：https://pan.baidu.com/s/1p4bTF8w_nw5pBieIr_EFyA 提取码：1234
     *
     * //前端使用方法
     * <script src="js/jsencrypt.js"></script>
     *     function encryptRequest( text) {
     *     var encrypt=new JSEncrypt();
     *     encrypt.setPrivateKey("公秘钥");
     *     //生成密文
     *     alert(encrypt.encrypt(text))
     * }
     */

    /**
     * 用于封装随机产生的公钥与私钥
     *
     * @author yihur
     * @date 2019/4/4
     * @param
     * @return
     */
    private static Map<Integer, String> keyMap = new HashMap<>();

    public static String publicKey() {
        return keyMap.get(0);  //0表示公钥
    }

    public static String privateKey() {
        return keyMap.get(1);  //1表示私钥
    }

    /**
     * 随机生成密钥对
     *
     * @param
     * @return void
     * @author yihur
     * @date 2019/4/4
     */
    public static void genKeyPair() {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = null;
        try {
            keyPairGen = KeyPairGenerator.getInstance("RSA");
        } catch (NoSuchAlgorithmException e) {
            throw new BizException(e);

        }
        // 初始化密钥对生成器，密钥大小为96-1024位
        assert keyPairGen != null;
        keyPairGen.initialize(1024, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String publicKeyString = Base64Util.encodeToString(publicKey.getEncoded());
        // 得到私钥字符串
        String privateKeyString = Base64Util.encodeToString((privateKey.getEncoded()));
        // 将公钥和私钥保存到Map
        keyMap.put(0, publicKeyString);  //0表示公钥
        keyMap.put(1, privateKeyString);  //1表示私钥
    }

    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @param publicKey 公钥
     * @return 密文
     */
    public static String encrypt(String str, String publicKey) {
        //base64编码的公钥
        byte[] decoded = Base64Util.decode(publicKey.getBytes(StandardCharsets.UTF_8));
        RSAPublicKey pubKey = null;
        String outStr = null;
        try {
            pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            outStr = Base64Util.encodeToString(cipher.doFinal(str.getBytes(StandardCharsets.UTF_8)));
        } catch (InvalidKeySpecException | BadPaddingException | IllegalBlockSizeException | InvalidKeyException |
                 NoSuchPaddingException | NoSuchAlgorithmException e) {
            throw new BizException(e);

        }
        //RSA加密
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @param privateKey 私钥
     * @return 铭文
     */
    public static String decrypt(String str, String privateKey) {
        //64位解码加密后的字符串
        byte[] inputByte = Base64Util.decode(str.getBytes(StandardCharsets.UTF_8));
        //base64编码的私钥
        byte[] decoded = Base64Util.decode(privateKey.getBytes(StandardCharsets.UTF_8));
        RSAPrivateKey priKey = null;
        //RSA解密
        Cipher cipher = null;
        String outStr = null;
        try {
            priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
            cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.DECRYPT_MODE, priKey);
            outStr = new String(cipher.doFinal(inputByte));
        } catch (InvalidKeySpecException | NoSuchAlgorithmException | NoSuchPaddingException | BadPaddingException |
                 IllegalBlockSizeException | InvalidKeyException e) {
            throw new BizException(e);

        }
        return outStr;
    }


}

